With continuous development of information technologies, software of a Computer Aided Design (CAD) graphic system has become an indispensable drawing tool of drawing personnel or designers. The capacities of storage devices are increased due to the improvement of the level of science and technology, and a designer usually draws many entities in a CAD drawing. Such a huge and dense set of entities has brought a big problem for a CAD system operator to select a single entity or some entities. The intensity of entities reduces the probability for a user to select a target entity. Such a problem is prominent especially on a mobile device. Since a screen of a common mobile device is relatively small, the pad of a finger seems relatively large when compared with the screen, it is less accurate and more difficult for the finger to select a target entity on a CAD finger system of the device.
Generally, an entity of a CAD figure can be processed by a control instruction in a CAD system. The control instruction can include a TRIM command (an entity trimming command), an offset command (an entity deleting command), a chamfer command (an entity copying command), a Mirror command (an entity mirroring command) and an Array command (an entity arraying command) and so on, and a processing flow of an existing control instruction includes several steps as follows.
First, a command function corresponding to the control instruction is invoked after the control instruction is inputted on a CAD platform.
Secondly, a user is prompted to select an entity, and the user selects a pickup point as required.
Thirdly, a system filters an entity according to a predetermined range of the pickup point, and uses an entity obtained through the filtering as a selected entity.
Finally, the control instruction performs corresponding processing to the selected entity, e.g. a TRIM command will trim the entity, an offset command will delete the entity from a drawing and so on.
It may be learned from the analysis above that all existing selecting methods and systems of a CAD graphic system use an entity selecting technology that a point where a finger leaves on a screen of a mobile device is used as a pickup point and an entity where the pickup point locates is determined and then used as a finally-selected entity. However, such selecting devices have many disadvantages. On one hand, existing screens of mobile devices are mostly capacitive screens and a point where a finger lifts to leave such screens deviates from a desired pickup point of a user, thus an entity obtained finally may not be expected by the user. On the other hand, most screens of mobile devices are touch screens, which are very inconvenient for selecting an entity with a finger. The pad of a finger, which occupies a large area on a screen, shields the user from observing an entity on the screen, thus it is difficult to select the entity, or a desirable entity can be hardly selected.
In addition, during existing methods for selecting an entity, an entity is not preselected in a selection process and the result of preselecting an entity is not displayed to a user, thus resulting a large finger coverage, and the user cannot be prompted that an entity will be selected when there are a plurality of entities in a finger selection area, thereby the user may select a wrong entity.
In addition, during a process of selecting an entity on a CAD platform of various devices, a user is incapable of foreseeing the final effect of a preselected entity processed by a control instruction, thus the user can learn whether a selected entity is satisfactory only after the selected entity is processed through the control instruction. If the selected entity is unsatisfactory, a wrong selection is proven and the user has to further execute a backspace command on the CAD platform to recover the entity to a state before the entity is processed by a command and reselect an entity, thus causing repeated selections to result in a lot of unnecessary work invisibly, which reduces working efficiency.
At present, there is no effective solution for a problem in the prior art that a processing process of a control instruction needs to be performed repeatedly and working efficiency is reduced because a user needs to recover a graphic entity to a state before processing when a processing result, which can be learned by the user only after the control instruction is executed during a process of processing the graphic entity with the control instruction of a graphic system, is unsatisfactory.